Reading data/variables
Hi, The obvious answer is don't use attach() and you'll never have that problem. And see further comments inline.
On Tue, Nov 15, 2011 at 6:05 PM, Steven Yen <syen at utk.edu> wrote:
Can someone help me with this variable/data reading issue?
I read a csv file and transform/create an additional variable (called y).
The first set of commands below produced different sample statistics
for hw11$y and y
In the second set of command I renameuse the variable name yy, and
sample statistics for $hw11$yy and yy are identical.
Using y <- yy fixed it, but I am not sure why I would need to do that.
That "y" appeared to have come from a variable called "y" from
another data frame (unrelated to the current run).
Help!
?> setwd("z:/homework")
?> sink ("z:/homework/hw11.our", append=T, split=T)
?> hw11 <- read.csv("ij10b.csv",header=T)
?> hw11$y <- hw11$e3
?> attach(hw11)
The following object(s) are masked _by_ '.GlobalEnv':
? ? y
Look there. R even *told* you that it was going to use the y in the global environment rather than the one you were trying to attach. The other solution: don't save your workspace. Your other email on this topic suggested to me that there is a .RData file in your preferred working directory that contains an object y, and that's what is interfering with what you think should happen. Deleting that file, or using a different directory, or removing y before you attach the data frame would all work. But truly, the best possible strategy is to avoid using attach() so you don't have to worry about which object named y is really being used because you specify it explicitly.
?> (n <- dim(hw11)[1])
[1] 13765
?> summary(hw11$y)
? ? Min. ?1st Qu. ? Median ? ? Mean ?3rd Qu. ? ? Max.
? 0.0000 ? 0.4500 ? 1.0000 ? 1.6726 ? 2.0000 140.0000
?> length(hw11$y)
[1] 13765
?> summary(y)
? ?Min. 1st Qu. ?Median ? ?Mean 3rd Qu. ? ?Max.
0.00000 0.00000 0.00000 0.24958 0.00000 1.00000
?> length(y)
[1] 601
?>
?> setwd("z:/homework")
?> sink ("z:/homework/hw11.our", append=T, split=T)
?> hw11 <- read.csv("ij10b.csv",header=T)
?> hw11$yy <- hw11$e3
?> attach(hw11)
?> hw11$yy <- hw11$e3
?> summary(hw11$yy)
? ? Min. ?1st Qu. ? Median ? ? Mean ?3rd Qu. ? ? Max.
? 0.0000 ? 0.4500 ? 1.0000 ? 1.6726 ? 2.0000 140.0000
?> length(hw11$yy)
[1] 13765
?> summary(yy)
? ? Min. ?1st Qu. ? Median ? ? Mean ?3rd Qu. ? ? Max.
? 0.0000 ? 0.4500 ? 1.0000 ? 1.6726 ? 2.0000 140.0000
?> length(yy)
[1] 13765
?>
Sarah Goslee http://www.functionaldiversity.org